The first equation is open, since it has an unsolvable variable. 1x could be anything!
The second equation is false, because 20 - 11 = 9 not 11.
The last equation is true, 7 + 10 does equal 17!
1x + 4 = 10
x = 10 - 4
x = 6 (true)
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20 - 11 = 11
20 - 11 = 9 (false)
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7 + 10 = 17 (true)
